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The grief-stricken family of an autistic Garfield High School student who drowned during a field trip called for an independent probe of the incident while also demanding Superintendent John Deasy's resignation. Ted Chen reports from East Los Angeles for the NBC4 News at 5 p.m. on Thursday, June 5, 2014. (Published Thursday, June 5, 2014)

Updated at 7:49 PM PDT on Thursday, Jun 5, 2014

The parents of a special needs student are looking for answers after their 16-year-old son with autism drowned Wednesday during a class field trip in East Los Angeles.

Lifeguards pulled Garfield High School student Erick Ortiz from the deep end of the pool at Atlantic Park. A witness said the lifeguard immediately began administering CPR.

Sister, Witness React to Teen's Drowning

The sister of a drowning victim and a witness talk about the events that led to the boy's death. Video broadcast Wednesday June 4, 2014 on NBC4. (Published Thursday, June 5, 2014)

"(Erick) went in with all of his clothes on, you know with his shoes on, this is not (how) somebody that’s prepared to go swimming goes into the pool, right?" Erick's sister Leslie Ortiz said.

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Leslie Ortiz said that a teaching assistant was assigned exclusively to her brother and that it was his job to be with Erick at all times.

"That was his one job, to watch him. Where was he? My brother couldn’t even go to the bathroom alone, the assistant had to go with him," Leslie Ortiz said.

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The Ortiz family was also concerned about how the teaching assistant handled the situation in the minutes that followed the drowning.

"(Erick's) own TA called my mom at 1:40 p.m. and told her that they were trying to revive him in the ambulance," Leslie Ortiz said. "Why didn’t he call her before? He waited until the ambulance was there to contact my mom. I don’t think that’s right."

Leslie Ortiz said that her mother fought with LAUSD to get her son that teaching assistant, knowing that Erick needed extra help.

"My mom went to the school every day. Took care of (Erick), dealt with every single teacher that he has," Leslie Ortiz said. "You could go to Garfield High School, everybody knows my mom, everybody knows her."

On Thursday morning, the Los Angeles Unified School District issued a statement regarding Erick's death.

"The District extends heartfelt condolences to the family on its tragic loss. The District will continue to cooperate with the ongoing law enforcement investigation. Crisis counselors are on site to help the school community. We will have no further comment at this time."

A flag outside the school was at half-staff Thursday morning, the final day of classes at Garfield High School.

Erick was one of five children – one girl and four boys. The Ortiz family says they cannot wrap their minds around how no one saw Erick enter the pool.

"Was my brother pushed, did he trip, did he fall in there? But I mean whatever the circumstance was, where was everybody around him that couldn’t see what happened?" Leslie Ortiz said. "There was a lot of people there."

Investigators were uncertain whether Ortiz jumped or was pushed into the pool.

"He went down toward the bottom of the pool, surfaced back up. Appeared to take a breath and then sank back down toward the bottom," said Lt. Eddie Hernandez of the Los Angeles County Sheriff’s Department.

Sheriff’s officials said parent permission is required for any student to take part in the annual field trip, Global Bash, and teachers accompany the children.

"My mom signed permission for him to go the park, not inside the pool," Leslie Ortiz said. "The assistant was aware that my brother did not know how to swim."

Witnesses said the field trip was cut short as the victim’s mother rushed to her son’s side.

“I heard screaming and I knew it was the mother because she was screaming for her son. Why, why did this happen to her son? Who wasn't watching him?” witness Ana Serrano said.

Attorney Luis Carrillo, who is representing the victim’s family, is accusing the Los Angeles Unified School District of negligence, saying the teaching assistant who was assigned full time to Ortiz since 2012 left him unattended.

“The family wants justice, an independent investigation and answers as to why their child was left alone. The family does not want condolences from the LAUSD,” Carillo said.

The family is asking for donations for the teen's funeral. Anyone who wishes to donate can donate to Bank of America account number 3250-4062-9139 with routing number 121000350.